/* 

  * tclLiteral.c --

  *

  *	Implementation of the global and ByteCode-local literal tables

  *	used to manage the Tcl objects created for literal values during

  *	compilation of Tcl scripts. This implementation borrows heavily

  *	from the more general hashtable implementation of Tcl hash tables

  *	that appears in tclHash.c.

  *

  * Copyright (c) 1997-1998 Sun Microsystems, Inc.

  *

  * See the file "license.terms" for information on usage and redistribution

  * of this file, and for a DISCLAIMER OF ALL WARRANTIES.

  *

  * RCS: @(#) $Id: tclLiteral.c,v 1.11 2001/10/11 22:28:01 msofer Exp $

  */

 #include "tclInt.h"

 #include "tclCompile.h"

 #include "tclPort.h"

 /*

  * When there are this many entries per bucket, on average, rebuild

  * a literal's hash table to make it larger.

  */

 #define REBUILD_MULTIPLIER	3

 /*

  * Procedure prototypes for static procedures in this file:

  */

 static int		AddLocalLiteralEntry _ANSI_ARGS_((

 			    CompileEnv *envPtr, LiteralEntry *globalPtr,

 			    int localHash));

 static void		ExpandLocalLiteralArray _ANSI_ARGS_((

 			    CompileEnv *envPtr));

 static unsigned int	HashString _ANSI_ARGS_((CONST char *bytes,

 			    int length));

 static void		RebuildLiteralTable _ANSI_ARGS_((

 			    LiteralTable *tablePtr));

 /*

  *----------------------------------------------------------------------

  *

  * TclInitLiteralTable --

  *

  *	This procedure is called to initialize the fields of a literal table

  *	structure for either an interpreter or a compilation's CompileEnv

  *	structure.

  *

  * Results:

  *	None.

  *

  * Side effects: 

  *	The literal table is made ready for use.

  *

  *----------------------------------------------------------------------

  */

 void

 TclInitLiteralTable(tablePtr)

     register LiteralTable *tablePtr; /* Pointer to table structure, which

 				      * is supplied by the caller. */

 {

 #if (TCL_SMALL_HASH_TABLE != 4) 

     panic("TclInitLiteralTable: TCL_SMALL_HASH_TABLE is %d, not 4\n",

 	    TCL_SMALL_HASH_TABLE);

 #endif

     tablePtr->buckets = tablePtr->staticBuckets;

     tablePtr->staticBuckets[0] = tablePtr->staticBuckets[1] = 0;

     tablePtr->staticBuckets[2] = tablePtr->staticBuckets[3] = 0;

     tablePtr->numBuckets = TCL_SMALL_HASH_TABLE;

     tablePtr->numEntries = 0;

     tablePtr->rebuildSize = TCL_SMALL_HASH_TABLE*REBUILD_MULTIPLIER;

     tablePtr->mask = 3;

 }

 /*

  *----------------------------------------------------------------------

  *

  * TclDeleteLiteralTable --

  *

  *	This procedure frees up everything associated with a literal table

  *	except for the table's structure itself.

  *

  * Results:

  *	None.

  *

  * Side effects:

  *	Each literal in the table is released: i.e., its reference count

  *	in the global literal table is decremented and, if it becomes zero,

  *	the literal is freed. In addition, the table's bucket array is

  *	freed.

  *

  *----------------------------------------------------------------------

  */

 void

 TclDeleteLiteralTable(interp, tablePtr)

     Tcl_Interp *interp;		/* Interpreter containing shared literals

 				 * referenced by the table to delete. */

     LiteralTable *tablePtr;	/* Points to the literal table to delete. */

 {

     LiteralEntry *entryPtr;

     int i, start;

     /*

      * Release remaining literals in the table. Note that releasing a

      * literal might release other literals, modifying the table, so we

      * restart the search from the bucket chain we last found an entry.

      */

 #ifdef TCL_COMPILE_DEBUG

     TclVerifyGlobalLiteralTable((Interp *) interp);

 #endif /*TCL_COMPILE_DEBUG*/

     start = 0;

     while (tablePtr->numEntries > 0) {

 	for (i = start;  i < tablePtr->numBuckets;  i++) {

 	    entryPtr = tablePtr->buckets[i];

 	    if (entryPtr != NULL) {

 		TclReleaseLiteral(interp, entryPtr->objPtr);

 		start = i;

 		break;

 	    }

 	}

     }

     /*

      * Free up the table's bucket array if it was dynamically allocated.

      */

     if (tablePtr->buckets != tablePtr->staticBuckets) {

 	ckfree((char *) tablePtr->buckets);

     }

 }

 /*

  *----------------------------------------------------------------------

  *

  * TclRegisterLiteral --

  *

  *	Find, or if necessary create, an object in a CompileEnv literal

  *	array that has a string representation matching the argument string.

  *

  * Results:

  *	The index in the CompileEnv's literal array that references a

  *	shared literal matching the string. The object is created if

  *	necessary.

  *

  * Side effects:

  *	To maximize sharing, we look up the string in the interpreter's

  *	global literal table. If not found, we create a new shared literal

  *	in the global table. We then add a reference to the shared

  *	literal in the CompileEnv's literal array. 

  *

  *	If onHeap is 1, this procedure is given ownership of the string: if

  *	an object is created then its string representation is set directly

  *	from string, otherwise the string is freed. Typically, a caller sets

  *	onHeap 1 if "string" is an already heap-allocated buffer holding the

  *	result of backslash substitutions.

  *

  *----------------------------------------------------------------------

  */

 int

 TclRegisterLiteral(envPtr, bytes, length, onHeap)

     CompileEnv *envPtr;		/* Points to the CompileEnv in whose object

 				 * array an object is found or created. */

     register char *bytes;	/* Points to string for which to find or

 				 * create an object in CompileEnv's object

 				 * array. */

     int length;			/* Number of bytes in the string. If < 0,

 				 * the string consists of all bytes up to

 				 * the first null character. */

     int onHeap;			/* If 1 then the caller already malloc'd

 				 * bytes and ownership is passed to this

 				 * procedure. */

 {

     Interp *iPtr = envPtr->iPtr;

     LiteralTable *globalTablePtr = &(iPtr->literalTable);

     LiteralTable *localTablePtr = &(envPtr->localLitTable);

     register LiteralEntry *globalPtr, *localPtr;

     register Tcl_Obj *objPtr;

     unsigned int hash;

     int localHash, globalHash, objIndex;

     long n;

     char buf[TCL_INTEGER_SPACE];

     if (length < 0) {

 	length = (bytes? strlen(bytes) : 0);

     }

     hash = HashString(bytes, length);

     /*

      * Is the literal already in the CompileEnv's local literal array?

      * If so, just return its index.

      */

     localHash = (hash & localTablePtr->mask);

     for (localPtr = localTablePtr->buckets[localHash];

 	  localPtr != NULL;  localPtr = localPtr->nextPtr) {

 	objPtr = localPtr->objPtr;

 	if ((objPtr->length == length) && ((length == 0)

 		|| ((objPtr->bytes[0] == bytes[0])

 			&& (memcmp(objPtr->bytes, bytes, (unsigned) length)

 				== 0)))) {

 	    if (onHeap) {

 		ckfree(bytes);

 	    }

 	    objIndex = (localPtr - envPtr->literalArrayPtr);

 #ifdef TCL_COMPILE_DEBUG

 	    TclVerifyLocalLiteralTable(envPtr);

 #endif /*TCL_COMPILE_DEBUG*/

 	    return objIndex;

 	}

     }

     /*

      * The literal is new to this CompileEnv. Is it in the interpreter's

      * global literal table?

      */

     globalHash = (hash & globalTablePtr->mask);

     for (globalPtr = globalTablePtr->buckets[globalHash];

 	 globalPtr != NULL;  globalPtr = globalPtr->nextPtr) {

 	objPtr = globalPtr->objPtr;

 	if ((objPtr->length == length) && ((length == 0)

 		|| ((objPtr->bytes[0] == bytes[0])

 			&& (memcmp(objPtr->bytes, bytes, (unsigned) length)

 				== 0)))) {

 	    /*

 	     * A global literal was found. Add an entry to the CompileEnv's

 	     * local literal array.

 	     */

 	    if (onHeap) {

 		ckfree(bytes);

 	    }

 	    objIndex = AddLocalLiteralEntry(envPtr, globalPtr, localHash);

 #ifdef TCL_COMPILE_DEBUG

 	    if (globalPtr->refCount < 1) {

 		panic("TclRegisterLiteral: global literal \"%.*s\" had bad refCount %d",

 			(length>60? 60 : length), bytes,

 			globalPtr->refCount);

 	    }

 	    TclVerifyLocalLiteralTable(envPtr);

 #endif /*TCL_COMPILE_DEBUG*/ 

 	    return objIndex;

 	}

     }

     /*

      * The literal is new to the interpreter. Add it to the global literal

      * table then add an entry to the CompileEnv's local literal array.

      * Convert the object to an integer object if possible.

      */

     TclNewObj(objPtr);

     Tcl_IncrRefCount(objPtr);

     if (onHeap) {

 	objPtr->bytes = bytes;

 	objPtr->length = length;

     } else {

 	TclInitStringRep(objPtr, bytes, length);

     }

     if (TclLooksLikeInt(bytes, length)) {

 	/*

 	 * From here we use the objPtr, because it is NULL terminated

 	 */

 	if (TclGetLong((Tcl_Interp *) NULL, objPtr->bytes, &n) == TCL_OK) {

 	    TclFormatInt(buf, n);

 	    if (strcmp(objPtr->bytes, buf) == 0) {

 		objPtr->internalRep.longValue = n;

 		objPtr->typePtr = &tclIntType;

 	    }

 	}

     }

 #ifdef TCL_COMPILE_DEBUG

     if (TclLookupLiteralEntry((Tcl_Interp *) iPtr, objPtr) != NULL) {

 	panic("TclRegisterLiteral: literal \"%.*s\" found globally but shouldn't be",

 	        (length>60? 60 : length), bytes);

     }

 #endif

     globalPtr = (LiteralEntry *) ckalloc((unsigned) sizeof(LiteralEntry));

     globalPtr->objPtr = objPtr;

     globalPtr->refCount = 0;

     globalPtr->nextPtr = globalTablePtr->buckets[globalHash];

     globalTablePtr->buckets[globalHash] = globalPtr;

     globalTablePtr->numEntries++;

     /*

      * If the global literal table has exceeded a decent size, rebuild it

      * with more buckets.

      */

     if (globalTablePtr->numEntries >= globalTablePtr->rebuildSize) {

 	RebuildLiteralTable(globalTablePtr);

     }

     objIndex = AddLocalLiteralEntry(envPtr, globalPtr, localHash);

 #ifdef TCL_COMPILE_DEBUG

     TclVerifyGlobalLiteralTable(iPtr);

     TclVerifyLocalLiteralTable(envPtr);

     {

 	LiteralEntry *entryPtr;

 	int found, i;

 	found = 0;

 	for (i = 0;  i < globalTablePtr->numBuckets;  i++) {

 	    for (entryPtr = globalTablePtr->buckets[i];

 		    entryPtr != NULL;  entryPtr = entryPtr->nextPtr) {

 		if ((entryPtr == globalPtr)

 		        && (entryPtr->objPtr == objPtr)) {

 		    found = 1;

 		}

 	    }

 	}

 	if (!found) {

 	    panic("TclRegisterLiteral: literal \"%.*s\" wasn't global",

 	            (length>60? 60 : length), bytes);

 	}

     }

 #endif /*TCL_COMPILE_DEBUG*/

 #ifdef TCL_COMPILE_STATS   

     iPtr->stats.numLiteralsCreated++;

     iPtr->stats.totalLitStringBytes   += (double) (length + 1);

     iPtr->stats.currentLitStringBytes += (double) (length + 1);

     iPtr->stats.literalCount[TclLog2(length)]++;

 #endif /*TCL_COMPILE_STATS*/

     return objIndex;

 }

 /*

  *----------------------------------------------------------------------

  *

  * TclLookupLiteralEntry --

  *

  *	Finds the LiteralEntry that corresponds to a literal Tcl object

  *      holding a literal.

  *

  * Results:

  *      Returns the matching LiteralEntry if found, otherwise NULL.

  *

  * Side effects:

  *      None.

  *

  *----------------------------------------------------------------------

  */

 LiteralEntry *

 TclLookupLiteralEntry(interp, objPtr)

     Tcl_Interp *interp;		/* Interpreter for which objPtr was created

                                  * to hold a literal. */

     register Tcl_Obj *objPtr;	/* Points to a Tcl object holding a

                                  * literal that was previously created by a

                                  * call to TclRegisterLiteral. */

 {

     Interp *iPtr = (Interp *) interp;

     LiteralTable *globalTablePtr = &(iPtr->literalTable);

     register LiteralEntry *entryPtr;

     char *bytes;

     int length, globalHash;

     bytes = Tcl_GetStringFromObj(objPtr, &length);

     globalHash = (HashString(bytes, length) & globalTablePtr->mask);

     for (entryPtr = globalTablePtr->buckets[globalHash];

             entryPtr != NULL;  entryPtr = entryPtr->nextPtr) {

         if (entryPtr->objPtr == objPtr) {

             return entryPtr;

         }

     }

     return NULL;

 }

 /*

  *----------------------------------------------------------------------

  *

  * TclHideLiteral --

  *

  *	Remove a literal entry from the literal hash tables, leaving it in

  *	the literal array so existing references continue to function.

  *	This makes it possible to turn a shared literal into a private

  *	literal that cannot be shared.

  *

  * Results:

  *	None.

  *

  * Side effects:

  *	Removes the literal from the local hash table and decrements the

  *	global hash entry's reference count.

  *

  *----------------------------------------------------------------------

  */

 void

 TclHideLiteral(interp, envPtr, index)

     Tcl_Interp *interp;		 /* Interpreter for which objPtr was created

                                   * to hold a literal. */

     register CompileEnv *envPtr; /* Points to CompileEnv whose literal array

 				  * contains the entry being hidden. */

     int index;			 /* The index of the entry in the literal

 				  * array. */

 {

     LiteralEntry **nextPtrPtr, *entryPtr, *lPtr;

     LiteralTable *localTablePtr = &(envPtr->localLitTable);

     int localHash, length;

     char *bytes;

     Tcl_Obj *newObjPtr;

     lPtr = &(envPtr->literalArrayPtr[index]);

     /*

      * To avoid unwanted sharing we need to copy the object and remove it from

      * the local and global literal tables.  It still has a slot in the literal

      * array so it can be referred to by byte codes, but it will not be matched

      * by literal searches.

      */

     newObjPtr = Tcl_DuplicateObj(lPtr->objPtr);

     Tcl_IncrRefCount(newObjPtr);

     TclReleaseLiteral(interp, lPtr->objPtr);

     lPtr->objPtr = newObjPtr;

     bytes = Tcl_GetStringFromObj(newObjPtr, &length);

     localHash = (HashString(bytes, length) & localTablePtr->mask);

     nextPtrPtr = &localTablePtr->buckets[localHash];

     for (entryPtr = *nextPtrPtr; entryPtr != NULL; entryPtr = *nextPtrPtr) {

 	if (entryPtr == lPtr) {

 	    *nextPtrPtr = lPtr->nextPtr;

 	    lPtr->nextPtr = NULL;

 	    localTablePtr->numEntries--;

 	    break;

 	}

 	nextPtrPtr = &entryPtr->nextPtr;

     }

 }

 /*

  *----------------------------------------------------------------------

  *

  * TclAddLiteralObj --

  *

  *	Add a single literal object to the literal array.  This

  *	function does not add the literal to the local or global

  *	literal tables.  The caller is expected to add the entry

  *	to whatever tables are appropriate.

  *

  * Results:

  *	The index in the CompileEnv's literal array that references the

  *	literal.  Stores the pointer to the new literal entry in the

  *	location referenced by the localPtrPtr argument.

  *

  * Side effects:

  *	Expands the literal array if necessary.  Increments the refcount

  *	on the literal object.

  *

  *----------------------------------------------------------------------

  */

 int

 TclAddLiteralObj(envPtr, objPtr, litPtrPtr)

     register CompileEnv *envPtr; /* Points to CompileEnv in whose literal

 				  * array the object is to be inserted. */

     Tcl_Obj *objPtr;		 /* The object to insert into the array. */

     LiteralEntry **litPtrPtr;	 /* The location where the pointer to the

 				  * new literal entry should be stored.

 				  * May be NULL. */

 {

     register LiteralEntry *lPtr;

     int objIndex;

     if (envPtr->literalArrayNext >= envPtr->literalArrayEnd) {

 	ExpandLocalLiteralArray(envPtr);

     }

     objIndex = envPtr->literalArrayNext;

     envPtr->literalArrayNext++;

     lPtr = &(envPtr->literalArrayPtr[objIndex]);

     lPtr->objPtr = objPtr;

     Tcl_IncrRefCount(objPtr);

     lPtr->refCount = -1;	/* i.e., unused */

     lPtr->nextPtr = NULL;

     if (litPtrPtr) {

 	*litPtrPtr = lPtr;

     }

     return objIndex;

 }

 /*

  *----------------------------------------------------------------------

  *

  * AddLocalLiteralEntry --

  *

  *	Insert a new literal into a CompileEnv's local literal array.

  *

  * Results:

  *	The index in the CompileEnv's literal array that references the

  *	literal.

  *

  * Side effects:

  *	Increments the ref count of the global LiteralEntry since the

  *	CompileEnv now refers to the literal. Expands the literal array

  *	if necessary. May rebuild the hash bucket array of the CompileEnv's

  *	literal array if it becomes too large.

  *

  *----------------------------------------------------------------------

  */

 static int

 AddLocalLiteralEntry(envPtr, globalPtr, localHash)

     register CompileEnv *envPtr; /* Points to CompileEnv in whose literal

 				  * array the object is to be inserted. */

     LiteralEntry *globalPtr;	 /* Points to the global LiteralEntry for

 				  * the literal to add to the CompileEnv. */

     int localHash;		 /* Hash value for the literal's string. */

 {

     register LiteralTable *localTablePtr = &(envPtr->localLitTable);

     LiteralEntry *localPtr;

     int objIndex;

     objIndex = TclAddLiteralObj(envPtr, globalPtr->objPtr, &localPtr);

     /*

      * Add the literal to the local table.

      */

     localPtr->nextPtr = localTablePtr->buckets[localHash];

     localTablePtr->buckets[localHash] = localPtr;

     localTablePtr->numEntries++;

     globalPtr->refCount++;

     /*

      * If the CompileEnv's local literal table has exceeded a decent size,

      * rebuild it with more buckets.

      */

     if (localTablePtr->numEntries >= localTablePtr->rebuildSize) {

 	RebuildLiteralTable(localTablePtr);

     }

 #ifdef TCL_COMPILE_DEBUG

     TclVerifyLocalLiteralTable(envPtr);

     {

 	char *bytes;

 	int length, found, i;

 	found = 0;

 	for (i = 0;  i < localTablePtr->numBuckets;  i++) {

 	    for (localPtr = localTablePtr->buckets[i];

 		    localPtr != NULL;  localPtr = localPtr->nextPtr) {

 		if (localPtr->objPtr == globalPtr->objPtr) {

 		    found = 1;

 		}

 	    }

 	}

 	if (!found) {

 	    bytes = Tcl_GetStringFromObj(globalPtr->objPtr, &length);

 	    panic("AddLocalLiteralEntry: literal \"%.*s\" wasn't found locally",

 	            (length>60? 60 : length), bytes);

 	}

     }

 #endif /*TCL_COMPILE_DEBUG*/

     return objIndex;

 }

 /*

  *----------------------------------------------------------------------

  *

  * ExpandLocalLiteralArray --

  *

  *	Procedure that uses malloc to allocate more storage for a

  *	CompileEnv's local literal array.

  *

  * Results:

  *	None.

  *

  * Side effects:

  *	The literal array in *envPtr is reallocated to a new array of

  *	double the size, and if envPtr->mallocedLiteralArray is non-zero

  *	the old array is freed. Entries are copied from the old array

  *	to the new one. The local literal table is updated to refer to

  *	the new entries.

  *

  *----------------------------------------------------------------------

  */

 static void

 ExpandLocalLiteralArray(envPtr)

     register CompileEnv *envPtr; /* Points to the CompileEnv whose object

 				  * array must be enlarged. */

 {

     /*

      * The current allocated local literal entries are stored between

      * elements 0 and (envPtr->literalArrayNext - 1) [inclusive].

      */

     LiteralTable *localTablePtr = &(envPtr->localLitTable);

     int currElems = envPtr->literalArrayNext;

     size_t currBytes = (currElems * sizeof(LiteralEntry));

     register LiteralEntry *currArrayPtr = envPtr->literalArrayPtr;

     register LiteralEntry *newArrayPtr =

 	    (LiteralEntry *) ckalloc((unsigned) (2 * currBytes));

     int i;

     /*

      * Copy from the old literal array to the new, then update the local

      * literal table's bucket array.

      */

     memcpy((VOID *) newArrayPtr, (VOID *) currArrayPtr, currBytes);

     for (i = 0;  i < currElems;  i++) {

 	if (currArrayPtr[i].nextPtr == NULL) {

 	    newArrayPtr[i].nextPtr = NULL;

 	} else {

 	    newArrayPtr[i].nextPtr = newArrayPtr

 		    + (currArrayPtr[i].nextPtr - currArrayPtr);

 	}

     }

     for (i = 0;  i < localTablePtr->numBuckets;  i++) {

 	if (localTablePtr->buckets[i] != NULL) {

 	    localTablePtr->buckets[i] = newArrayPtr

 	            + (localTablePtr->buckets[i] - currArrayPtr);

 	}

     }

     /*

      * Free the old literal array if needed, and mark the new literal

      * array as malloced.

      */

     if (envPtr->mallocedLiteralArray) {

 	ckfree((char *) currArrayPtr);

     }

     envPtr->literalArrayPtr = newArrayPtr;

     envPtr->literalArrayEnd = (2 * currElems);

     envPtr->mallocedLiteralArray = 1;

 }

 /*

  *----------------------------------------------------------------------

  *

  * TclReleaseLiteral --

  *

  *	This procedure releases a reference to one of the shared Tcl objects

  *	that hold literals. It is called to release the literals referenced

  *	by a ByteCode that is being destroyed, and it is also called by

  *	TclDeleteLiteralTable.

  *

  * Results:

  *	None.

  *

  * Side effects:

  *	The reference count for the global LiteralTable entry that 

  *	corresponds to the literal is decremented. If no other reference

  *	to a global literal object remains, it is freed.

  *

  *----------------------------------------------------------------------

  */

 void

 TclReleaseLiteral(interp, objPtr)

     Tcl_Interp *interp;		/* Interpreter for which objPtr was created

 				 * to hold a literal. */

     register Tcl_Obj *objPtr;	/* Points to a literal object that was

 				 * previously created by a call to

 				 * TclRegisterLiteral. */

 {

     Interp *iPtr = (Interp *) interp;

     LiteralTable *globalTablePtr = &(iPtr->literalTable);

     register LiteralEntry *entryPtr, *prevPtr;

     ByteCode* codePtr;

     char *bytes;

     int length, index;

     bytes = Tcl_GetStringFromObj(objPtr, &length);

     index = (HashString(bytes, length) & globalTablePtr->mask);

     /*

      * Check to see if the object is in the global literal table and 

      * remove this reference.  The object may not be in the table if

      * it is a hidden local literal.

      */

     for (prevPtr = NULL, entryPtr = globalTablePtr->buckets[index];

 	    entryPtr != NULL;

 	    prevPtr = entryPtr, entryPtr = entryPtr->nextPtr) {

 	if (entryPtr->objPtr == objPtr) {

 	    entryPtr->refCount--;

 	    /*

 	     * If the literal is no longer being used by any ByteCode,

 	     * delete the entry then remove the reference corresponding 

 	     * to the global literal table entry (decrement the ref count 

 	     * of the object).

 	     */

 	    if (entryPtr->refCount == 0) {

 		if (prevPtr == NULL) {

 		    globalTablePtr->buckets[index] = entryPtr->nextPtr;

 		} else {

 		    prevPtr->nextPtr = entryPtr->nextPtr;

 		}

 		ckfree((char *) entryPtr);

 		globalTablePtr->numEntries--;

 		TclDecrRefCount(objPtr);

 		/*

 		 * Check if the LiteralEntry is only being kept alive by 

 		 * a circular reference from a ByteCode stored as its 

 		 * internal rep. In that case, set the ByteCode object array 

 		 * entry NULL to signal to TclCleanupByteCode to not try to 

 		 * release this about to be freed literal again.

 		 */

 		if (objPtr->typePtr == &tclByteCodeType) {

 		    codePtr = (ByteCode *) objPtr->internalRep.otherValuePtr;

 		    if ((codePtr->numLitObjects == 1)

 		            && (codePtr->objArrayPtr[0] == objPtr)) {			

 			codePtr->objArrayPtr[0] = NULL;

 		    }

 		}

 #ifdef TCL_COMPILE_STATS

 		iPtr->stats.currentLitStringBytes -= (double) (length + 1);

 #endif /*TCL_COMPILE_STATS*/

 	    }

 	    break;

 	}

     }

     /*

      * Remove the reference corresponding to the local literal table

      * entry.

      */

     Tcl_DecrRefCount(objPtr);

 }

 /*

  *----------------------------------------------------------------------

  *

  * HashString --

  *

  *	Compute a one-word summary of a text string, which can be

  *	used to generate a hash index.

  *

  * Results:

  *	The return value is a one-word summary of the information in

  *	string.

  *

  * Side effects:

  *	None.

  *

  *----------------------------------------------------------------------

  */

 static unsigned int

 HashString(bytes, length)

     register CONST char *bytes; /* String for which to compute hash

 				 * value. */

     int length;			/* Number of bytes in the string. */

 {

     register unsigned int result;

     register int i;

     /*

      * I tried a zillion different hash functions and asked many other

      * people for advice.  Many people had their own favorite functions,

      * all different, but no-one had much idea why they were good ones.

      * I chose the one below (multiply by 9 and add new character)

      * because of the following reasons:

      *

      * 1. Multiplying by 10 is perfect for keys that are decimal strings,

      *    and multiplying by 9 is just about as good.

      * 2. Times-9 is (shift-left-3) plus (old).  This means that each

      *    character's bits hang around in the low-order bits of the

      *    hash value for ever, plus they spread fairly rapidly up to

      *    the high-order bits to fill out the hash value.  This seems

      *    works well both for decimal and non-decimal strings.

      */

     result = 0;

     for (i = 0;  i < length;  i++) {

 	result += (result<<3) + *bytes++;

     }

     return result;

 }

 /*

  *----------------------------------------------------------------------

  *

  * RebuildLiteralTable --

  *

  *	This procedure is invoked when the ratio of entries to hash buckets

  *	becomes too large in a local or global literal table. It allocates

  *	a larger bucket array and moves the entries into the new buckets.

  *

  * Results:

  *	None.

  *

  * Side effects:

  *	Memory gets reallocated and entries get rehashed into new buckets.

  *

  *----------------------------------------------------------------------

  */

 static void

 RebuildLiteralTable(tablePtr)

     register LiteralTable *tablePtr; /* Local or global table to enlarge. */

 {

     LiteralEntry **oldBuckets;

     register LiteralEntry **oldChainPtr, **newChainPtr;

     register LiteralEntry *entryPtr;

     LiteralEntry **bucketPtr;

     char *bytes;

     int oldSize, count, index, length;

     oldSize = tablePtr->numBuckets;

     oldBuckets = tablePtr->buckets;

     /*

      * Allocate and initialize the new bucket array, and set up

      * hashing constants for new array size.

      */

     tablePtr->numBuckets *= 4;

     tablePtr->buckets = (LiteralEntry **) ckalloc((unsigned)

 	    (tablePtr->numBuckets * sizeof(LiteralEntry *)));

     for (count = tablePtr->numBuckets, newChainPtr = tablePtr->buckets;

 	    count > 0;

 	    count--, newChainPtr++) {

 	*newChainPtr = NULL;

     }

     tablePtr->rebuildSize *= 4;

     tablePtr->mask = (tablePtr->mask << 2) + 3;

     /*

      * Rehash all of the existing entries into the new bucket array.

      */

     for (oldChainPtr = oldBuckets;

 	    oldSize > 0;

 	    oldSize--, oldChainPtr++) {

 	for (entryPtr = *oldChainPtr;  entryPtr != NULL;

 	        entryPtr = *oldChainPtr) {

 	    bytes = Tcl_GetStringFromObj(entryPtr->objPtr, &length);

 	    index = (HashString(bytes, length) & tablePtr->mask);

 	    *oldChainPtr = entryPtr->nextPtr;

 	    bucketPtr = &(tablePtr->buckets[index]);

 	    entryPtr->nextPtr = *bucketPtr;

 	    *bucketPtr = entryPtr;

 	}

     }

     /*

      * Free up the old bucket array, if it was dynamically allocated.

      */

     if (oldBuckets != tablePtr->staticBuckets) {

 	ckfree((char *) oldBuckets);

     }

 }

 #ifdef TCL_COMPILE_STATS

 /*

  *----------------------------------------------------------------------

  *

  * TclLiteralStats --

  *

  *	Return statistics describing the layout of the hash table

  *	in its hash buckets.

  *

  * Results:

  *	The return value is a malloc-ed string containing information

  *	about tablePtr.  It is the caller's responsibility to free

  *	this string.

  *

  * Side effects:

  *	None.

  *

  *----------------------------------------------------------------------

  */

 char *

 TclLiteralStats(tablePtr)

     LiteralTable *tablePtr;	/* Table for which to produce stats. */

 {

 #define NUM_COUNTERS 10

     int count[NUM_COUNTERS], overflow, i, j;

     double average, tmp;

     register LiteralEntry *entryPtr;

     char *result, *p;

     /*

      * Compute a histogram of bucket usage. For each bucket chain i,

      * j is the number of entries in the chain.

      */

     for (i = 0;  i < NUM_COUNTERS;  i++) {

 	count[i] = 0;

     }

     overflow = 0;

     average = 0.0;

     for (i = 0;  i < tablePtr->numBuckets;  i++) {

 	j = 0;

 	for (entryPtr = tablePtr->buckets[i];  entryPtr != NULL;

 	        entryPtr = entryPtr->nextPtr) {

 	    j++;

 	}

 	if (j < NUM_COUNTERS) {

 	    count[j]++;

 	} else {

 	    overflow++;

 	}

 	tmp = j;

 	average += (tmp+1.0)*(tmp/tablePtr->numEntries)/2.0;

     }

     /*

      * Print out the histogram and a few other pieces of information.

      */

     result = (char *) ckalloc((unsigned) ((NUM_COUNTERS*60) + 300));

     sprintf(result, "%d entries in table, %d buckets\n",

 	    tablePtr->numEntries, tablePtr->numBuckets);

     p = result + strlen(result);

     for (i = 0; i < NUM_COUNTERS; i++) {

 	sprintf(p, "number of buckets with %d entries: %d\n",

 		i, count[i]);

 	p += strlen(p);

     }

     sprintf(p, "number of buckets with %d or more entries: %d\n",

 	    NUM_COUNTERS, overflow);

     p += strlen(p);

     sprintf(p, "average search distance for entry: %.1f", average);

     return result;

 }

 #endif /*TCL_COMPILE_STATS*/

 #ifdef TCL_COMPILE_DEBUG

 /*

  *----------------------------------------------------------------------

  *

  * TclVerifyLocalLiteralTable --

  *

  *	Check a CompileEnv's local literal table for consistency.

  *

  * Results:

  *	None.

  *

  * Side effects:

  *	Panics if problems are found.

  *

  *----------------------------------------------------------------------

  */

 void

 TclVerifyLocalLiteralTable(envPtr)

     CompileEnv *envPtr;		/* Points to CompileEnv whose literal

 				 * table is to be validated. */

 {

     register LiteralTable *localTablePtr = &(envPtr->localLitTable);

     register LiteralEntry *localPtr;

     char *bytes;

     register int i;

     int length, count;

     count = 0;

     for (i = 0;  i < localTablePtr->numBuckets;  i++) {

 	for (localPtr = localTablePtr->buckets[i];

 	        localPtr != NULL;  localPtr = localPtr->nextPtr) {

 	    count++;

 	    if (localPtr->refCount != -1) {

 		bytes = Tcl_GetStringFromObj(localPtr->objPtr, &length);

 		panic("TclVerifyLocalLiteralTable: local literal \"%.*s\" had bad refCount %d",

 		        (length>60? 60 : length), bytes,

 		        localPtr->refCount);

 	    }

 	    if (TclLookupLiteralEntry((Tcl_Interp *) envPtr->iPtr,

 		    localPtr->objPtr) == NULL) {

 		bytes = Tcl_GetStringFromObj(localPtr->objPtr, &length);

 		panic("TclVerifyLocalLiteralTable: local literal \"%.*s\" is not global",

 		         (length>60? 60 : length), bytes);

 	    }

 	    if (localPtr->objPtr->bytes == NULL) {

 		panic("TclVerifyLocalLiteralTable: literal has NULL string rep");

 	    }

 	}

     }

     if (count != localTablePtr->numEntries) {

 	panic("TclVerifyLocalLiteralTable: local literal table had %d entries, should be %d",

 	      count, localTablePtr->numEntries);

     }

 }

 /*

  *----------------------------------------------------------------------

  *

  * TclVerifyGlobalLiteralTable --

  *

  *	Check an interpreter's global literal table literal for consistency.

  *

  * Results:

  *	None.

  *

  * Side effects:

  *	Panics if problems are found.

  *

  *----------------------------------------------------------------------

  */

 void

 TclVerifyGlobalLiteralTable(iPtr)

     Interp *iPtr;		/* Points to interpreter whose global

 				 * literal table is to be validated. */

 {

     register LiteralTable *globalTablePtr = &(iPtr->literalTable);

     register LiteralEntry *globalPtr;

     char *bytes;

     register int i;

     int length, count;

     count = 0;

     for (i = 0;  i < globalTablePtr->numBuckets;  i++) {

 	for (globalPtr = globalTablePtr->buckets[i];

 	        globalPtr != NULL;  globalPtr = globalPtr->nextPtr) {

 	    count++;

 	    if (globalPtr->refCount < 1) {

 		bytes = Tcl_GetStringFromObj(globalPtr->objPtr, &length);

 		panic("TclVerifyGlobalLiteralTable: global literal \"%.*s\" had bad refCount %d",

 		        (length>60? 60 : length), bytes,

 		        globalPtr->refCount);

 	    }

 	    if (globalPtr->objPtr->bytes == NULL) {

 		panic("TclVerifyGlobalLiteralTable: literal has NULL string rep");

 	    }

 	}

     }

     if (count != globalTablePtr->numEntries) {

 	panic("TclVerifyGlobalLiteralTable: global literal table had %d entries, should be %d",

 	      count, globalTablePtr->numEntries);

     }

 }

 #endif /*TCL_COMPILE_DEBUG*/